As an ecologist and biodiversity researcher and recorder, the author visits a wide range of rural and urban habitats mainly close to his home in Sedlescombe near Hastings, East Sussex, UK. The weblog covers the full spectrum of wildlife, from mammals to microbes. As well as details of encounters with England’s flora and fauna, information on where to see species of interest is often given.

Friday, April 29, 2011

Alder buckthorn (Frangula alnus) is an unassuming shrub or small tree that is not uncommon in woods and on heaths in England and Wales. Its main claim to attention today is that it is one of the principle food plants of the brimstone butterfly (Gonepteryx rhamni) but it has had an important role in the past in the fortunes of this and other European countries through the use of its charcoal in the manufacture of gunpowder. Alder buckthorn charcoal ignites readily and burns evenly and slowly. As well as for cartridges, its steady-burning properties were exploited in manufacturing fuses for explosives (Mauskopf, 2006).

Alder buckthorn grows quite widely in my home area around the village of Sedlescombe in East Sussex, UK, mostly occurring in woodlands. I have come across a few plants, in Brede High Wood for example, that appear to have been coppiced, but I think coppice plantations of this small tree were not established locally in the past. However, as the following paragraphs will indicate, it seems highly likely that the wood was harvested as a valuable item of underwood for converting to gunpowder charcoal, either locally or further afield.

The value of alder buckthorn charcoal for gunpowder dates back many years and it has been described as being of “major military importance in the 15th to 19th centuries.” (Mobile Reference, 2010). In 1785 Major William Congreve (later Sir William) carried out tests on the charcoal from various woods and in 1791 listed alder buckthorn (as black dogwood), alder and white willow as the best types to be used in gunpowder production. Writing in 1831, Elizabeth Kent said that the charcoal made from the wood was “much prized by the manufacturers of gunpowder, who buy up all they can procure of it, and use it only for the very best gunpowder.”

Part of the reason why the economic role of alder buckthorn was obscured is that its vernacular names were confusing. John R. Jackson, curator of the museum at Kew, wrote in 1870 “In most books relating to economic botany, or to the application of woods,Cornus sanguinea, or dogwood, is referred to as yielding the best charcoal for gunpowder. Certain it is that the gunpowder makers all know the wood they use in such large quantities, by the name of dogwood, and it was generally believed that Cornus sanguinea was the plant which furnished them with their supplies.” At that period, samples of ‘dogwood’ used for gunpowder charcoal in many different places were sent to Kew and all turned out to be alder buckthorn. Jackson continued that this was proof that alder buckthorn “is the plant from whence the gunpowder-makers draw their supplies, and that Cornus sanguinea, or true dogwood, is never used, now, nor, indeed is there any proof that it ever has been, for the powder makers maintain that what they now call dogwood is the same wood which has always been used by them.”

This confusion of names has been compounded by the scientific name of alder buckthorn changing from Rhamnus frangula to Frangula alnus in the last century.

Alder buckthorn is uncommon in Scotland but, in about 1870, the Royal Botanic Gardens, Edinburgh was sent a sample of alder buckthorn (as dogwood) from the Roslin Gunpowder Mills of Hay, Merricks & Co. in Midlothian. It was “of English growth in the county of Sussex” where the price varied from £10 to £14 per ton, according to quality. The sticks, which were usually sent out in May or June, were peeled and packed into bundles of 100 (M’Nab, 1870).

The Merricks family, who established the Roslin Gunpowder Mill in about 1805, originated in East Sussex “near the gunpowder mill sites at Battle and Sedlescombe” though no evidence has been found that any of the Merricks worked at these mills (Crocker, 1996). However, it may be that they took a knowledge of alder buckthorn charcoal with them to Scotland plus a knowledge of how to procure it.

In her book about Sedlescombe, Beryl Lucy (1978) says “the charcoal for ordinary gunpowder was made from alder wood burnt in pits in the way that had been practised locally, in Petley Woods in particular, from time immemorial. For the finer or sporting powder, dogwood was used. Both of these woods are still very plentiful in our countryside. When the underwood in the district was being cut, the dogwood was carefully reserved, peeled and tied into bundles.” Alder buckthorn is not uncommon today in the Petley Wood area of Sedlescombe, while true dogwood (Cornus sanguinea) does not occur naturally in this part of East Sussex.

Another important gunpowder mill was that of John Hall & Son at Faversham in Kent and they apparently worked in conjunction with Hay, Merricks and Co., of Roslin to produce the only explosives of the gunpowder type which successfully passed the Woolwich tests for the " Permitted List." (International Congress of Pure and Applied Chemistry, 1909).

Hall’s works at Faversham spread over six hundred acres planted with both alder and alder buckthorn “more especially of the former, for though the wood itself is not so valuable as the latter for the actual manufacture of powder, the tree is, owing to its larger size, more effectual in obstructing fragments of burning timber as well as diminishing the force of the shock in case of an explosion.” (Jackson, 1870).

As an illustration of the quality and importance of alder buckthorn charcoal, Mauskopf (2006) writes “Fine Grain powder was replaced by Enfield Rifle (E.R.) powder in 1859; the grain size of the new powder was increased from 16-36 mesh to 16-24 mesh. But the chief modification was the change of wood for the charcoal: ‘dogwood’ was substituted for alder or willow. In a footnote to this passage Mauskopf, referring to a Major Morgan of the Royal Artillery, writes “The substitute was, in fact, alder buckthorn (Rhamnus frangula), known in France as bourdaine, the traditional source of charcoal for French military powder. Since the comparative on gunpowder of the chemist J.-L. Proust, published early in the century, bourdaine was known to yield a strong powder.”

In the earlier part of the 19th century alder buckthorn was obtained chiefly from Suffolk, Norfolk, Essex and Kent (Jackson, 1870) “but after the introduction of the Enfield rifle into the military service of this country, the superior kinds of powder came much more into demand, and it was found difficult to obtain a sufficient quantity.” Because of this, supplies of the wood were imported from mainland Europe, particularly Holland, Germany and Belgium. The charcoal was prepared in enclosed iron cylinders (Saturday Magazine, 1886).

During World War I the difficulty of obtaining alder buckthorn charcoal from mainland Europe meant that supplies had to be sought within Britain. The War Office appealed for wood in Gardeners’ Chronicle in 1915 saying they “would be glad to know of any supplies of Rhamnus Frangula in this country. Estate owners who have plantations of Rhamnus and are willing to sell should communicate with the Secretary, War Office, Whitehall.” (Anon., 1915) This was followed in the same magazine a few months later by a longer article from E. M. Holmes, a pharmacist and botanist from Sevenoaks, Kent. He said, among other things (Holmes, 1915):

· The wood of this small tree is at present much wanted for the manufacture of fine gunpowder. Formerly it was imported from Germany, where apparently the tree was coppiced in order to get straight stems.

· Wood about one inch in diameter is required.

· Those who know where the tree grows in fair abundance should make known the fact.

· The wood is recognised by the manufacturer by having a reddish stain around the small pith which the wood of Cornus does not possess.

· The bark, when scratched with the finger nail or a knife blade, shows a crimson colour underneath. .

· In view of the present difficulty experience should teach the necessity of cultivating Rhamnus Frangula in woods in this country.

Charcoal from alder buckthorn remained important for munitions until the close of World War II. According to Meiggs (1949):

"The Home Timber Production Department undertook responsibility for the supply of alder buckthorn (Rhamnus frangula) needed for the manufacture of a highly specialised form of charcoal used in the making of certain types of explosive. Before the war supplies had come from France and Czechoslovakia, but in 1938 small scale orders had been placed with the Forestry Commission and had been met from the New Forest. .... It was ... plentiful enough in the New Forest for economic production and it was in the New Forest that the first war demands were met and the basis of the standard organisation laid.

The sticks were cut in 2½-foot lengths, bundled in the woods and brought to a picking up point from which they were transported to a central depot. The sticks had to be peeled, which could only be done easily while the sap was up in the spring. As the demand increased, however, production had to be maintained over the whole year; outside the natural peeling season, the sticks were first boiled in a copper for up to an hour to make peeling easier and then laid out for two or three days to dry, before being again bundled, weighed and despatched. The same organisation was repeated when new depots were opened and women made this small but important sphere their own. The operations at the depot were organised by a specially selected measurer and the peeling and other work of the depot was carried out entirely by women. Women also eventually became exclusively responsible for locating supplies in the woods and for supervising the cutting to ensure that the cutters made no mistakes in identifying the somewhat rare shrub.

The demand grew rapidly as the munition programme got into its stride. Only 50 tons had been ordered in 1939. The requirement for 1940 was 200 tons, increased in 1941 to 400 tons, and fresh areas had to be opened up. Wicken Fen was the first outside the New Forest to be exploited, and following a survey of East Anglia, operations were extended to the neighbouring counties. In 1941, since these two main sources were becoming exhausted, a complete survey was made of the country by the Cambridge School of Botany for the Biology War Committee. Much useful information was gathered in the course of this survey on the ecological habits of the plant and the areas of main concentration were tabulated. ....

With the extension of operations a new peeling depot was established in the north west, drawing supplies from the neighbouring Divisions, but by the middle of 1943 sufficient stocks had been built up to call a halt."

Despite the value and importance of its charcoal, alder buckthorn seldom seems to have been grown as a crop in Britain, most supplies being gathered from self-sown plants scattered through the underwood. Sir Joseph Hooker, director of Kew Gardens in the late 19th century, did recommend that it was grown on a coppice system and this seems to have happened in the Faversham area, but this was almost certainly the exception rather than the rule. In some places today the plant is particularly abundant, Broadwater Forest near Tunbridge Wells, for example. This area was much used by the military in the past and it may be that the tree was deliberately encouraged.

In addition to its importance for gunpowder charcoal, alder buckthorn had a role in medecine and in the production of the artist's pigment known as sap green. Kent (1831) wrote “The juice expressed from the berries being boiled down with some gum arabic and a little alum, and then poured into bladders to grow hard, is the colour called sap green.”

Alder buckthorn bark and berries have long been used as a powerful laxative. Though this largely seemed to have stopped during the 19thcentury as gentler aperients became available, the bark was used for its purgative properties during World War II. Meiggs (1949) wrote “The bark was dried on corrugated iron sheets over improvised burners and ultimately found its way into purgatives. This was no secret to the gypsies who for centuries have eaten the berries or chewed the bark of alder buckthorn in preference to the more expensive and synthetic purgatives provided by the chemist; the use of the bark for this purpose, however, only became a respectable war demand when other sources of supply were reduced.”

Mauskopf, S. H. (2005) Chemistry in the Arsenal: State regulation and scientific methodology gunpowder in eighteenth-century England and France. In Steele, Brett D. &Dorland, Tamara. Eds.(2005) The heirs of Archimedes: science and the art of war through the Age of Enlightenment. MIT, Cambridge, Massachusetts.